Update: If you are running HP UPD 5.3 then perform an upgrade to 5.4.
Not a direct solutions this time, but the info underneath will point you in a direction..
Errors from UmRdpService in the log files, possible cause is the HP Universal Print Driver.
See the last post of this thread: http://social.technet.microsoft.com/Forums/en-US/winserverTS/thread/deecfbbb-369d-4225-a2d2-58ce54977d58/ It gives a good detail on information about a possible cause.
Read some post with recommendations for hotfix http://support.microsoft.com/kb/2457866 on this error, we’ll do a test.
Other people state that a ICA connection with lots of redirected printers could cause this problem…
Also read enabling RDS Easy Print by GPO solves some issues…
And maybe test disabling the HP Universal Print Driver Services.. (The HPZ12 Net AND HPZ12 PML Service)
As always, Test,test & accept before production.